VSE. I need to rotate image with arbitrary center pivot point that is not in the center of the image
It is possible friend, just follow these steps 


import your image file in Blender VSE
click image offset 


 


Another step should be adding your transform strip to it but this is the place where you go wrong so before adding transform strip change these values by the formula - 


x dimension =  (video dimension x - file dimension x)/2

y dimension =  (video dimension y - file dimension y)/2  

so here my video dimensions are - (1920,1080) 



and my image dimension are - (620,387)



so I will change these values -


to x = (1920-620)/2 = 650
   Y = (1080-387)/2 = 347



so what we did here is all because to put the pivot point of image file in center.

now add your transform strip and rotate 

 

Now it will rotate from center
you can change the x and Y points of your transform strip to position your image anywhere but do not change the X Y points of original file .....Use transform strip only to position and rotation.